What Is Nearshore Nourishment? A Cost-Effective Way to Protect Beaches
- Aaron Salyer
- Sep 8, 2023
- 4 min read
Nearshore nourishment is a coastal management technique where sand is placed in the active nearshore zone, rather than pumped directly onto the dry beach. Once placed, waves and currents gradually move the sand shoreward, helping to widen the beach profile and reduce erosion risk over time.
For suitable sites, nearshore nourishment can be a cost-effective way to support beach recovery, improve coastal resilience and make better use of offshore sand reserves or navigation dredging material. It can also reduce disruption to beach users compared with traditional pump-ashore nourishment.
ICM has been involved in the development, design and monitoring of nearshore nourishment since the early Gold Coast trials in the 1980s. These projects helped show how placed sand can behave like a natural storm bar, moving within the active beach system and contributing to beach recovery.
Why Nearshore Nourishment Was Developed
Nearshore nourishment was developed as a practical response to the need for large-scale beach nourishment at a lower cost. On the Gold Coast, early onshore nourishment campaigns showed that placing sand directly on the beach could be effective, but also expensive and disruptive during construction.
In 1985, nearshore nourishment was trialled on the Gold Coast using offshore sand reserves. Instead of placing all the sand directly onto the beach, part of the material was placed offshore in the active nearshore zone. Monitoring showed that the sand could remain within the beach system and move shoreward under suitable wave conditions.
ICM founder Angus Jackson was closely involved in these early investigations and trials. The work helped shape a practical method that has since been used on the Gold Coast and other exposed coastlines where suitable sand sources, wave conditions and placement depths are available.
Watch the video below to learn more about ICM’s role in the development of nearshore nourishment on the Gold Coast.
How does Nearshore Nourishment Work?
Nearshore nourishment works by placing sand within the active beach profile. The aim is to place sand where natural wave action can move it landward over time. In this way, nearshore nourishment can mimic the behaviour of natural storm bars, which form offshore during erosion events and later migrate back toward the beach during calmer conditions.
What Dredge is used for Nearshore Nourishment
Nearshore nourishment is commonly carried out using a trailing suction hopper dredger (TSHD). This type of dredge is often used for port and navigation channel dredging and can operate in exposed coastal conditions where swell is present.
A TSHD can place sand in several ways, depending on the project objectives, water depth, vessel draft and site conditions:
Bottom Dumping: sand is released through doors in the base of the vessel and placed in the nearshore zone. This is generally the lowest-cost placement method where the dredge can safely access the target depth.
Rainbowing: sand is sprayed from the vessel toward shallower water. This can place sand closer to the beach or surf zone, but is generally slower and more expensive than bottom dumping.
Pumping: It can pump material through a floating pipeline for precise placement.
The dredge collects sand from an approved source area, stores it in its hopper, then sails to the placement area. The sand is then discharged using the selected placement method. The right method depends on the sand source, sea conditions, target placement depth, environmental controls and cost.
The Benefits of Nearshore Nourishment
Nearshore nourishment can provide several benefits when applied in the right setting:
Lower placement costs: bottom dumping and rainbowing are generally less expensive than pumping sand directly onto the beach.
Reduced beach disruption: works can often be carried out offshore, reducing impacts on beach access, beach users and local businesses.
Works with natural processes: the method relies on waves and currents to move sand within the active beach system.
Use of offshore or dredged sand sources: suitable sand from offshore reserves or navigation dredging can be used where approvals and sediment quality requirements are met.
Potential surf amenity benefits: in some cases, placement can be designed to create temporary surfing benefits as sand moves through the nearshore zone.
Nearshore Nourishment as a Nature-Based Solution
Nearshore nourishment is often considered a nature-based coastal protection method because it adds sediment to the coastal system and relies on natural wave and sediment transport processes to distribute that sand. Rather than fixing the shoreline in place, it supports the beach’s ability to adjust and recover over time.
However, nearshore nourishment is not suitable for every site. It requires a clear understanding of wave climate, sediment transport, sand source quality, closure depth, environmental approvals, dredge access and monitoring requirements. The best outcomes occur when the method is designed as part of a broader coastal management strategy, rather than as a one-off emergency response.
Where Nearshore Nourishment Fits in Coastal Management
Nearshore nourishment is one tool within a broader coastal management strategy. It can be used alongside beach monitoring, sand bypassing, dune management, artificial reefs, artificial headlands, seawalls and other coastal protection measures, depending on the site.
For councils and coastal managers, the key question is not whether nearshore nourishment is always the right solution. The key question is whether the local coastal processes, sand sources, dredging access, environmental conditions and project objectives make it a suitable option.
ICM supports clients through this process by assessing coastal behaviour, identifying feasible sand sources, developing placement strategies, managing approvals and designing monitoring programs to track performance over time.
Learn More
For an in-depth review of the history of nearshore nourishment, the trials and monitoring over specific projects and more, check out the published works by Angus Jackson and Bobbie Corbett, which were presented at the Australasian Coast and Ports Conference in 2023.
